Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v4 1/6] lib/nmi_backtrace: explicitly serialize banner and regs | Date | Thu, 15 Jul 2021 21:39:54 +0206 |
| |
Currently the nmi_backtrace is serialized against other CPUs because the messages are sent to the NMI buffers. Once these buffers are removed, only the dumped stack will be serialized against other CPUs (via the printk_cpu_lock).
Also serialize the nmi_backtrace banner and regs using the printk_cpu_lock so that per-CPU serialization will be preserved even after the NMI buffers are removed.
Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> --- lib/nmi_backtrace.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c index 8abe1870dba4..dae233c5f597 100644 --- a/lib/nmi_backtrace.c +++ b/lib/nmi_backtrace.c @@ -92,17 +92,24 @@ module_param(backtrace_idle, bool, 0644); bool nmi_cpu_backtrace(struct pt_regs *regs) { int cpu = smp_processor_id(); + unsigned long flags; if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) { pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n", cpu, (void *)instruction_pointer(regs)); } else { + /* + * Allow nested NMI backtraces while serializing + * against other CPUs. + */ + printk_cpu_lock_irqsave(flags); pr_warn("NMI backtrace for cpu %d\n", cpu); if (regs) show_regs(regs); else dump_stack(); + printk_cpu_unlock_irqrestore(flags); } cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask)); return true; -- 2.20.1
| |